Variable-resistance medium for telephones



.UNITED'USTATES. PATENT OFFICE.

WILLIAM W. JACQUES, OF NEWTON, ASSIGNOR 'ro THE AMERICAN BELL TELEPHONE COMPANY, OF BOSTON, MASSACHUSETTS.

VARIABLE-RESlSTA NCE MEDIUM FOR TELEPHONE'S.

SPECIFICATION forming part of Letters Patent No. 524,172, dated August '7, 1894. I Application filed May 14, 1894:. Serial No. 511,239. (No specimens.)

Toall whom it may concern:

Be it known that 1, WILLIAM W. JACQUES, of'Newton, in the State of Massachusetts,have invented a new and useful Variable-Resistance Medium for Use between the Electrodes of Battery-Telephone Transmitters, of which 7 The'process consists in reducing a salt of boron by heating it with sodium or potassium and again heating the product .to a white heat in the absence of air..-

I take boracic acid and fuse it at-a white heat until it assumes the appearance of agate. I

then .pulverize it and mix it with metallic sodium or potassium in proper proportions to reduce the boracic acid. The mixture is then heated in a closed vessel, care being taken to prevent the access of air. After cooling, the

mixture is dissolved in water and filtered,

thus producing amorphous boron. This when dried at a reddish white heat in the absence of air produces electric and microphonic boron in granular condition. The grains form an ex- 2. The herein described process of producing a variable resistance medium for battery telephones consisting in reducing a salt of boron by heating it with sodium or potassium, and againheating the product to a white heat in the absence of air.

Witnesses:

WILLIAM W. SWAN, WILLIAM SUL IVAN.

WILLIAM W. JACQUES. 

